The invasive rodents, thought to have arrived along with whalers and buccaneers in the 17th century, feed on the eggs and young of the Galapagos’ many native residents, including giant tortoises, lava lizards, snakes, and iguanas. The rats are also known to feed on the plants that make up their food supply. “It's one of the worst problems the Galapagos have,” said Juan Carlos Gonzalez, a specialist with the Nature Conservancy. “[Rats] reproduce every three months and eat everything.”

The specially-designed poison, developed by Bell Laboratories in the Unites States, comes in the form of a one-centimeter-square cube that attracts rats but repulses the other species on the islands. The poison also contains a special anti-coagulant that will dry out the rat’s corpse and disintegrate it in a matter of days without a stench.

Park officials have begun trapping animals in order to keep them from eating the poisoned rats during the cull. They will be released again in early January.